尝试将Python dict附加到JSON时,它仅写入一次 [英] While trying to append Python dict to JSON it writes only once
问题描述
我正在进行人脸识别项目,并希望将检测到的人脸日志记录到JSON文件中.我正在使用以下代码.
I am working on a Face Recognition project and want to write logs of detected faces, into a JSON file. I am using the following code.
import os
import json
from datetime import datetime,date
now = datetime.strftime(datetime.now(), '%Y%m%d')
now_str = str(now)
def write_logs(time,date,name,accuracy,direction):
a = []
entry = {'time':time,'name':name,'accuracy':accuracy,'direction':direction}
if not os.path.isfile('./log'+now_str+'.json'):
a.append(entry)
with open('./log'+now_str+'.json', mode='a+') as f:
json.dump(a,f, indent=3)
return a
输出为:
[
{
"time": "13/06/2018 - 20:39:07",
"name": "Rajkiran",
"accuracy": "97.22941",
"direction": "default"
}
]
但是,我期望的是:
[
{
"time": "13/06/2018 - 20:39:07",
"name": "Rajkiran",
"accuracy": "97.22941",
"direction": "default"
},
{
"time": "13/06/2018 - 20:39:07",
"name": "Rajkiran",
"accuracy": "97.22941",
"direction": "default"
},
{
"time": "13/06/2018 - 20:39:07",
"name": "Rajkiran",
"accuracy": "97.22941",
"direction": "default"
}
]
应该连续添加JSON数组,直到我的算法识别出当天的面孔为止.但是,如前所述,它只写入一次.
The JSON arrays should be appended continuously, till the time my algorithm recognizes faces for the day. However, as mentioned earlier, it writes only once.
推荐答案
@RAJKIRAN VELDUR:问题是您的if语句.根据您的代码,文件一旦存在,就无法追加.我相信您只需要从if语句中删除not
,或完全删除if语句.根据您要完成的任务,您实际上并不需要它.
@RAJKIRAN VELDUR: The problem is your if-statement. According to your code, once the file exists, you cannot append to it. I believe you just need to remove not
from your if-statement, or remove the if-statement altogether. Based on what you're trying to accomplish, you don't actually need it.
编辑:json
模块不允许您以所需的方式附加到文件.最直接的方法是每次您要追加时加载和更新数据.像这样:
The json
module doesn't allow you to append to a file in the way that you want. The most straightforward approach will be to load and update the data each time you want to append. Like so:
def write_logs(time,date,name,accuracy,direction):
entry = {'time':time,'name':name,'accuracy':accuracy,'direction':direction}
log_file = './log'+now_str+'.json'
if not os.path.exists(log_file):
# Create file with JSON enclosures
with open(log_file, mode='w') as f:
json.dump([], f)
# The file already exists, load and update it
with open(log_file, 'r') as r:
data = json.load(r)
data.append(entry)
# Write out updated data
with open(log_file, mode='w') as f:
json.dump(data, f, indent=3)
return [entry]
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